scholarly journals The Reliability of Antarctic Tropospheric Pressure and Temperature in the Latest Global Reanalyses

2012 ◽  
Vol 25 (20) ◽  
pp. 7138-7146 ◽  
Author(s):  
Thomas J. Bracegirdle ◽  
Gareth J. Marshall
Keyword(s):  
Surface Energy Balance ◽  
Surface Air Temperature ◽  
Radiosonde Data ◽  
Positive Trend ◽  
Forecast System ◽  
Climate Forecast System ◽  
Sea Level Pressure ◽  
Climate Forecast System Reanalysis ◽  
Near Surface ◽  
Modern Era

Abstract In this study, surface and radiosonde data from staffed Antarctic observation stations are compared to output from five reanalyses [Climate Forecast System Reanalysis (CFSR), 40-yr ECMWF Re-Analysis (ERA-40), ECMWF Interim Re-Analysis (ERA-Interim), Japanese 25-year Reanalysis (JRA-25), and Modern Era Retrospective-Analysis for Research and Applications (MERRA)] over three decades spanning 1979–2008. Bias and year-to-year correlation between the reanalyses and observations are assessed for four variables: mean sea level pressure (MSLP), near-surface air temperature (Ts), 500-hPa geopotential height (H500), and 500-hPa temperature (T500). It was found that CFSR and MERRA are of a sufficiently high resolution for the height of the orography to be accurately reproduced at coastal observation stations. Progressively larger negative Ts biases at these coastal stations are apparent for reanalyses in order of decreasing resolution. However, orography height bias cannot explain large winter warm biases in CFSR, JRA-25, and MERRA (11.1°, 10.2°, and 7.9°C, respectively) at Amundsen–Scott and Vostok, which have been linked to problems with representing the surface energy balance. Linear trends in the annual-mean T500 and H500 averaged over Antarctica as a whole were found to be most reliable in CFSR, ERA-Interim, and MERRA, none of which show significant trends over the period 1979–2008. In contrast JRA-25 shows significant negative trends over 1979–2008 and ERA-40 gives significant positive trends during the 1980s (evident in both T500 and H500). Comparison to observations indicates that the positive trend in ERA-40 is spurious. At the smaller spatial scale of individual stations all five reanalyses have some spurious trends. However, ERA-Interim was found to be the most reliable for MSLP and H500 trends at station locations.

A Comparison of Extratropical Cyclones in Recent Reanalyses ERA-Interim, NASA MERRA, NCEP CFSR, and JRA-25

2011 ◽  
Vol 24 (18) ◽  
pp. 4888-4906 ◽  
Author(s):  
K. I. Hodges ◽  
R. W. Lee ◽  
L. Bengtsson
Keyword(s):  
The Other ◽  
Extratropical Cyclones ◽  
Forecast System ◽  
Climate Forecast System ◽  
Climate Forecast System Reanalysis ◽  
Spatial Differences ◽  
The Mean ◽  
Using Data ◽  
Modern Era ◽  
Ncep Climate Forecast System

Abstract Extratropical cyclones are identified and compared using data from four recent reanalyses for the winter periods in both hemispheres. Results show the largest differences occur between the older lower resolution 25-yr Japanese Reanalysis (JRA-25) when compared with the newer high resolution reanalyses, particularly in the Southern Hemisphere (SH). Spatial differences between the newest reanalyses are small in both hemispheres and generally not significant except in some common regions associated with cyclogenesis close to orography. Differences in the cyclone maximum intensitites are generally related to spatial resolution except in the NASA Modern Era Retrospective-Analysis for Research and Applications (NASA MERRA), which has larger intensities for several different measures. Matching storms between reanalyses shows the number matched between the ECMWF Interim Re-Analysis (ERA-Interim) and the other reanalyses is similar in the Northern Hemisphere (NH). In the SH the number matched between JRA-25 and ERA-Interim is lower than in the NH; however, for NASA MERRA and the NCEP Climate Forecast System Reanalysis (NCEP CFSR), the number matched is similar to the NH. The mean separation of the identically same cyclones is typically less than 2° geodesic in both hemispheres for the latest reanalyses, whereas JRA-25 compared with the other reanalyses has a broader distribution in the SH, indicating greater uncertainty. The instantaneous intensity differences for matched storms shows narrow distributions for pressure, while for winds and vorticity the distributions are much broader, indicating larger uncertainty typical of smaller-scale fields. Composite cyclone diagnostics show that cyclones are very similar between the reanalyses, with differences being related to the intensities, consistent with the intensity results. Overall, results show NH cyclones correspond well between reanalyses, with a significant improvement in the SH for the latest reanalyses, indicating a convergence between reanalyses for cyclone properties.

scholarly journals A 10-yr Climatology of Tibetan Plateau Vortices with NCEP Climate Forecast System Reanalysis

2014 ◽  
Vol 53 (1) ◽  
pp. 34-46 ◽  
Author(s):  
Xinyuan Feng ◽  
Changhai Liu ◽  
Roy Rasmussen ◽  
Guangzhou Fan
Keyword(s):  
Tibetan Plateau ◽  
Effective Diameter ◽  
Climate Forecast ◽  
Forecast System ◽  
Climate Forecast System ◽  
Climate Forecast System Reanalysis ◽  
Average Life Span ◽  
Near Surface ◽  
Late Night ◽  
Ncep Climate Forecast System

AbstractA plateau vortex refers to a shallow meso-α-scale cyclonic vortex that is usually confined to near-surface levels (500 hPa) over the Tibetan Plateau during warm seasons. It is the major precipitation-producing weather system over the plateau, but the knowledge of its climatology and understanding of generation mechanisms are limited because of the lack of adequate observations in this harsh mountainous region. In this study, the high-resolution NCEP Climate Forecast System Reanalysis data have been used to perform a statistical survey of these vortices over 10 warm seasons (April–October of 2000–09). The purpose is to document their climatological features, including genesis, size, life cycle, propagation, and diurnal variation.Results show that ~103 plateau vortices occur on average every year. Most are detected from May through August, with the maximum monthly count in July. The primary area of origin exhibits a west–east orientation in correspondence with a large-scale confluence zone, and the most concentrated source lies in the area of 33°–36°N, 84°–90°E in the high elevated central and western plateau. Significant diurnal variations are observed, characteristic of a preferential genesis during late afternoon to evening hours and a late night dissipation peak. The vortex events have an average life span of ~15 h and an average horizontal dimension (effective diameter) of ~280 km. In accordance with the steering environmental flow, an overwhelming majority travel eastward with a mean translation speed of ~10 m s−1. A small fraction of systems (approximately nine cases annually) move off the plateau, predominantly from the eastern edge.

scholarly journals Development and Application of a Hot-Dry-Windy Index (HDW) Climatology

Atmosphere ◽  
2018 ◽  
Vol 9 (7) ◽  
pp. 285 ◽  
Author(s):  
Jessica McDonald ◽  
Alan Srock ◽  
Joseph Charney
Keyword(s):  
Climatic Conditions ◽  
Classification Systems ◽  
Forecast System ◽  
Short Term ◽  
Climate Forecast System ◽  
Climate Forecast System Reanalysis ◽  
Near Surface ◽  
Geographical Variations ◽  
Weather Forecasters ◽  
Insight Into

In this paper, we describe and analyze a climatology of the Hot-Dry-Windy Index (HDW), with the goal of providing fire-weather forecasters with information about the daily and seasonal variability of the index. The 30-year climatology (1981–2010) was produced using the Climate Forecast System Reanalysis (CFSR) for the contiguous United States, using percentiles to show seasonal and geographical variations of HDW contained within the climatology. The method for producing this climatology is documented and the application of the climatology to historical fire events is discussed. We show that the HDW climatology provides insight into near-surface climatic conditions that can be used to identify temperature and humidity trends that correspond to climate classification systems. Furthermore, when used in conjunction with daily traces of HDW values, users can follow trends in HDW and compare those trends with historical values at a given location. More usefully, this climatology adds value to HDW forecasts; by combining the CFSR climatology and a Global Ensemble Forecast System (GEFS) ensemble history and forecast, we can produce a single product that provides seasonal, climatological, and short-term context to help determine the appropriate fire-management response to a given HDW value.

Sea Surface Temperature–Precipitation Relationship in Different Reanalyses

2013 ◽  
Vol 141 (3) ◽  
pp. 1118-1123 ◽  
Author(s):  
Arun Kumar ◽  
Li Zhang ◽  
Wanqiu Wang
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Time Scales ◽  
Department Of Energy ◽  
Sea Surface ◽  
Climate Forecast System ◽  
Climate Forecast System Reanalysis ◽  
Temperature And Precipitation ◽  
The Relationship ◽  
Modern Era

Abstract The focus of this investigation is how the relationship at intraseasonal time scales between sea surface temperature and precipitation (SST–P) varies among different reanalyses. The motivation for this work was spurred by a recent report that documented that the SST–P relationship in Climate Forecast System Reanalysis (CFSR) was much closer to that in the observation than it was for the older generation of reanalyses [i.e., NCEP–NCAR reanalysis (R1) and NCEP–Department of Energy (DOE) reanalysis (R2)]. Further, the reason was attributed either to the fact that the CFSR is a partially coupled reanalysis, while R1 and R2 are atmospheric-alone reanalyses, or that R1 and R2 use the observed weekly-averaged SST. The authors repeated the comparison of the SST–P relationship among R1, R2, and CFSR, as well as two recent generations of atmosphere-alone reanalyses, the Modern-Era Retrospective Analysis for Research and Applications (MERRA) and the ECMWF Re-Analysis Interim (ERA-Interim). The results clearly demonstrate that the differences in the SST–P relationship at intraseasonal time scales across different reanalyses are not due to whether the reanalysis system is coupled or atmosphere alone, but are due to the specification of different SSTs. The SST–P relationship in different reanalyses, when computed against a single SST for the benchmark, demonstrates a relationship that is common across all of the reanalyses and observations.

scholarly journals Reanalysis of 44 Yr of Climate in the French Alps (1958–2002): Methodology, Model Validation, Climatology, and Trends for Air Temperature and Precipitation

2009 ◽  
Vol 48 (3) ◽  
pp. 429-449 ◽  
Author(s):  
Yves Durand ◽  
Martin Laternser ◽  
Gérald Giraud ◽  
Pierre Etchevers ◽  
Bernard Lesaffre ◽  
...  
Keyword(s):  
Air Temperature ◽  
Numerical Models ◽  
Surface Air Temperature ◽  
Positive Trend ◽  
Mountain Areas ◽  
Near Surface ◽  
French Alps ◽  
Mountainous Regions ◽  
Temperature And Precipitation ◽  
Analysis Scheme

Abstract Since the early 1990s, Météo-France has used an automatic system combining three numerical models to simulate meteorological parameters, snow cover stratification, and avalanche risk at various altitudes, aspects, and slopes for a number of mountainous regions in France. Given the lack of sufficient directly observed long-term snow data, this “SAFRAN”–Crocus–“MEPRA” (SCM) model chain, usually applied to operational avalanche forecasting, has been used to carry out and validate retrospective snow and weather climate analyses for the 1958–2002 period. The SAFRAN 2-m air temperature and precipitation climatology shows that the climate of the French Alps is temperate and is mainly determined by atmospheric westerly flow conditions. Vertical profiles of temperature and precipitation averaged over the whole period for altitudes up to 3000 m MSL show a relatively linear variation with altitude for different mountain areas with no constraint of that kind imposed by the analysis scheme itself. Over the observation period 1958–2002, the overall trend corresponds to an increase in the annual near-surface air temperature of about 1°C. However, variations are large at different altitudes and for different seasons and regions. This significantly positive trend is most obvious in the 1500–2000-m MSL altitude range, especially in the northwest regions, and exhibits a significant relationship with the North Atlantic Oscillation index over long periods. Precipitation data are diverse, making it hard to identify clear trends within the high year-to-year variability.

Climatic characteristics of drift ice in the northern Barents Sea

2019 ◽  
Vol 11 (3) ◽  
pp. 800-811
Author(s):  
Chenglin Duan ◽  
Sheng Dong ◽  
Zhifeng Wang ◽  
Zhenkun Liao
Keyword(s):  
Barents Sea ◽  
Ice Thickness ◽  
Climate Forecast ◽  
Forecast System ◽  
Climate Forecast System ◽  
Climate Forecast System Reanalysis ◽  
Ice Velocity ◽  
Environmental Prediction ◽  
Climatic Characteristics

Abstract In this paper, a preliminary climatic description of the long-term offshore drift ice characteristics in the northern Barents Sea has been investigated from 1987 to 2016 based on the satellite ice motion datasets from National Snow and Ice Data Center (NSIDC) and reanalysis ice thickness datasets from National Centers for Environmental Prediction (NCEP)-Climate Forecast System Reanalysis (CFSR) and Climate Forecast System Version 2 (CFSv2). Both the ice velocity and thickness conditions have been studied at the three fixed locations from west to east. Annual and monthly drift ice roses indicate that the directions from WSW to SE are primarily prevailing, particularly in winter months. Besides, the annual ice speed extremums exceeding 40 cm s–1 mostly occur in the southerly directions from November to April. For the ice thickness, results reveal that it is prominently distributed in a thicker interval between 70 and 120 cm, and a thinner interval between 20 and 70 cm. The annual thickness maxima approximately range from 90 to 170 cm, primarily occurring from May to June, and demonstrate a light decreasing trend.

scholarly journals Evaluation of the Climate Forecast System Reanalysis weather data for the hydrological model in the Arctic watershed Målselv

2021 ◽  
Author(s):  
Minh Tuan Bui ◽  
Jinmei Lu ◽  
Linmei Nie
Keyword(s):  
High Resolution ◽  
Hydrological Model ◽  
The Arctic ◽  
Annual Rainfall ◽  
Climate Forecast ◽  
Hydrological Models ◽  
Forecast System ◽  
Climate Forecast System ◽  
Climate Forecast System Reanalysis

Abstract The high-resolution Climate Forecast System Reanalysis (CFSR) data have recently become an alternative input for hydrological models in data-sparse regions. However, the quality of CFSR data for running hydrological models in the Arctic is not well studied yet. This paper aims to compare the quality of CFSR data with ground-based data for hydrological modeling in an Arctic watershed, Målselv. The QSWAT model, a coupling of the hydrological model SWAT (soil and water assessment tool) and the QGIS, was applied in this study. The model ran from 1995 to 2012 with a 3-year warm-up period (1995–1997). Calibration (1998–2007), validation (2008–2012), and uncertainty analyses were conducted by the model for each dataset at five hydro-gauging stations within the watershed. The objective function Nash–Sutcliffe coefficient of efficiency for calibration is 0.65–0.82 with CFSR data and 0.55–0.74 with ground-based data, which indicate higher performance of the high-resolution CFSR data than the existing scattered ground-based data. The CFSR weather grid points showed higher variation in precipitation than the ground-based weather stations across the whole watershed. The calculated average annual rainfall by CFSR data for the whole watershed is approximately 24% higher than that by ground-based data, which results in some higher water balance components. The CFSR data also demonstrate its high capacities to replicate the streamflow hydrograph, in terms of timing and magnitude of peak and low flow. Through examination of the uncertainty coefficients P-factors (≥0.7) and R-factors (≤1.5), this study concludes that CFSR data are a reliable source for running hydrological models in the Arctic watershed Målselv.

Sign in / Sign up

Export Citation Format

Share Document